IIRC there are two registries that it’s worth joining in the UK, and you can apply to join one of them online and the other whenever you donate blood:
http://www.anthonynolan.org/8-ways-you-could-save-life/donate-your-stem-cells/apply-join-our-register
http://www.nhsbt.nhs.uk/bonemarrow/qa/index.asp#howcan
This appears to be the place to sign up in Canada:
https://www.blood.ca/en/stem-cells
(It seems that in some countries the term to search for is “stem cell donation for leukaemia” or somesuch.)
IIRC there are two registries that it’s worth joining in the UK, and you can apply to join one of them online and the other whenever you donate blood:
http://www.anthonynolan.org/8-ways-you-could-save-life/donate-your-stem-cells/apply-join-our-register
http://www.nhsbt.nhs.uk/bonemarrow/qa/index.asp#howcan
This appears to be the place to sign up in Canada:
https://www.blood.ca/en/stem-cells
(It seems that in some countries the term to search for is “stem cell donation for leukaemia” or somesuch.)